The calorie is a unit of energy defined as the amount of energy needed to raise 1 g of water by 1degree c. how many calories are required to bring a pot of water at 1degree c to a boil? the pot is full to the brim, with diameter 20 cm and depth 20 cm. the density of water is 1000 kg/m3. if we consider d for the pot to be 20 cm, approximately how much more energy is needed to heat a hot tub with d=2 m? how many calories is that? if energy costs 10 cents per kilowatt hour, how much does it cost to heat this hot tub? how does the price (in dollars) of heating the hot tub scale with the tub's characteristic dimension? what percentage of the cost of heating the tub would be saved by reducing the tub's characteristic dimension by 33%?

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

hi,

what occurs during a solar eclipse?

there are small tides across earth.

the moon is between earth and the sun.

p.s. im not sure if the first answer is correct because during a solar ecliphse there are spring tides and i dont know if they are the same.